Occurrence of Alternaria secondary metabolites in milling oats and its de-hulled fractions from harvest years 2017 to 2021.

In this study, secondary metabolites produced by Alternaria were investigated for their presence in milling oats. For this purpose, pre-cleaned milling oat samples (n = 193), intended for human consumption, out of harvest years 2017 to 2021 originating from different northern European countries were analysed by LC-MS/MS. Alternariol and alternariol methyl ether were positively identified in 38% of the samples with mean values of 2.1 µg/kg and 1.2 µg/kg, respectively. The highest concentrations of 50.5 µg/kg alternariol and 24.2 µg/kg of alternariol methyl ether were detected in a Latvian sample. Tenuazonic acid was found in 45% of all samples, with a mean concentration of 28.9 µg/kg and a maximum concentration of 1430 µg/kg, also in a Latvian sample. Tentoxin was detected in 49% of all samples with a mean value of 1.7 µg/kg. The Alternaria metabolite most frequently detected in 96% of all samples was infectopyrone with a mean concentration of 593 µg/kg and a maximum value reaching up to 3990 µg/kg in a German sample. In addition, eight oat samples were selected to investigate to what extent the Alternaria metabolites are distributed between the oat hulls and the oat kernels. After de-hulling, approximately 23% of Alternaria metabolites were found in the remaining oat kernels. According to the results, alternariol, infectopyrone and altersetin were present in the kernels with the lowest proportion of 10%-20% on average, respectively. The values for tentoxin showed that about 60% of tentoxin was contained in the hulls, while almost 40% remained in the oat kernel. This suggests that potential health risks posed by Alternaria secondary metabolites and metabolites of other fungal genera in milling oats can be reduced by de-hulling.

Reduction of deoxynivalenol, T-2 and HT-2 toxins and associated Fusarium species during commercial and laboratory de-hulling of milling oats.

Oats (Avena sativa L.) are well known for their nutritional properties but are susceptible to the growth of different Fusarium fungi resulting in mycotoxin contamination of harvested oats. In this study, oat samples from harvest years 2011 to 2017 were preselected for their suitability as milling oats for food purposes with DON contents below 1750 µg/kg. The reduction of DON, T-2 and HT-2 toxins during the commercial de-hulling process was analysed. While the average reduction for the sum of T-2 and HT-2 toxins in large oat kernels was 85%, the reduction for thin kernels was 66%. The reduction for DON was about 60% and did not differ for the two kernel fractions. In laboratory de-hulling experiments, milling oat samples and de-hulled oat kernels with known DON, T-2 and HT-2 toxin content were correlated with the associated DNA amount of Fusarium graminearum, Fusarium culmorum and Fusarium langsethiae. The reduction of the Fusarium DNA amount after de-hulling was comparable to the reduction of the associated mycotoxins. Notably, the correlation between F. langsethiae DNA amounts and the sum of T-2 and HT-2 toxin contents was R2 = 0.69 in milling oats and it rose to R2 = 0.85 in de-hulled oat kernels. In laboratory tests, at least one third of the initial levels of DON and the sum of T-2 and HT-2 toxins could be removed by polishing off the first parts of the outer layers; two thirds remained in the polished oat kernels. These observations indicate that de-hulling alone may not be completely sufficient to remove mycotoxin contamination in oats. These findings are of high importance in the discussion of determining legal maximum levels for DON or the sum of T-2 and HT-2 toxins in intermediate and final products.

Survey of mycotoxins in milling oats dedicated for food purposes between 2013 and 2019 by LC-MS/MS.

Although the common oat (Avena sativa L.) is well known for its nutritional benefits, it carries the risk of contamination with mycotoxins due to its susceptibility to the growth of various fungi. The procurement of milling oats for food could become more difficult in the coming harvest years due to limited availability, specific quality requirements and the avoidance of mycotoxin contamination. In light of ongoing discussions in the European Commission on regulatory limits for certain mycotoxins including their modified forms, the purpose of this study was to improve the database on their occurrence in milling oats. In particular, we provide data on the predominantly occurring trichothecenes such as deoxynivalenol and its acetylated and modified derivatives (e.g. 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol and deoxynivalenol-3-glucoside) as well as on T-2 and HT-2 toxins. Additionally, the following mycotoxins were analysed: zearalenone, nivalenol, diacetoxyscirpenol, fusarenon-X, ochratoxin A, sterigmatocystin and aflatoxins B1, B2, G1 and G2. Oat samples, (n = 281) pre-selected for their physical properties and DON-content to be less than 1750 µg/kg from 11 European provenances, were analysed for 16 different mycotoxins by LC-MS/MS. Samples were collected from the years of harvest 2013 to 2019. High incidence rates above the limit of quantification of either 5 µg/kg for T-2 and HT-2 toxins or 10 µg/kg for deoxynivalenol were found (98.1, 94.7 and 91.4%, respectively). The mean concentration of the sum of T-2 and HT-2 toxins was 149 µg/kg. The highest level was found in an Irish sample containing 1290 µg/kg for the sum of T-2 and HT-2 toxins. The mean deoxynivalenol concentration was 289 µg/kg, while the highest level was 1414 µg/kg in a Swedish sample. Besides nivalenol other mycotoxins were only present in trace concentrations or not detected.